Electrical Response Elicitted by Hyper–Accelerated Carbon Ion Irradiation

Abstract

Abstract: : Purpose: To determine whether hyper–accelerated carbon ion irradiation will elicit an electrical response from the eyes of mice. Methods: Eight week–old C57BL mice were deeply anesthetized by an intramuscular injection of a mixture of ketamine, xylazine, and urethane. A milky–white contact lens with an embedded gold electrode was placed on the anesthetized cornea as the active electrode. A needle electrode was inserted subcutaneously on the nasal bone as a reference electrode, and the ground electrode was placed subcutaneously in the neck region. The bandpass of the preamplifier was set between 1.5 to 40 Hz. Carbon ion particles were accelerated to 290 MeV to stimulate the eye. No absorber was placed between the accelerator and the eye. Approximately 1.0x10⁷ carbon particles were irradiated in circle of 10 cm diameter, and 1.0 x 10⁴ particles/sec were delivered to the eye. The duration of irradiation was 1.9 second. For control, ERGs elicited by light stimuli were recorded. The luminance was 2000 cd/m² and the duration was 1.9 sec. A scintillator sensor was placed close to the eye and responses from the eye and scintillator were recorded simultaneously. Results: With carbon particle irradiation, a slow positive wave appeared after the onset of the irradiation. The potential level then gradually decreased, and after the offset of carbon particle irradiation, a slow negative wave was seen similar to that following photic stimulation. Conclusions: An electrical response can be elicited from the eye by carbon ion irradiation. Further studies are necessary to investigate the origin of this response.

Keywords: electrophysiology: non-clinical • radiation therapy • retina